Field of the Invention
The present invention relates to a light source unit including a luminescent plate on to which excitation light from an excitation light source is shone and a projector including this light source unit.
Description of the Related Art
In these days, data projectors are used on many occasions as an image projection system which projects an image of a screen of a personal computer or a video image, as well as images based on image data which is stored on a memory card on to a screen. In these data projectors, light emitted from a light source is caused to converge to a micromirror display device called a DMD (Digital Micromirror Device) or a liquid crystal panel so that a full-color image is displayed onto a screen.
The Japanese Unexamined Patent Application No. 2013-47793 (Patent Literature 1) discloses a projector which includes an excitation light shining device which has blue laser diodes. Excitation light from this excitation light shining device is shone on to a luminescent material layer of a luminescent wheel, and light in the green wavelength range is emitted therefrom. The Japanese Unexamined Patent Application No. 2010-198805 (Patent Literature 2) discloses a projector which includes a light source unit in which excitation light is shone onto a plate-shaped luminescent material device which is formed by sintering an inorganic binder of a light transmitting inorganic material and a luminescent material to thereby obtain light in the green wavelength range. The Japanese Unexamined Patent Publication No. 2012-185980 (Patent Literature 3) discloses a wavelength changing device having a wavelength changing member made up of a sintered material of mixed powder which contains inorganic luminescent material powder and glass powder and a projector which includes this wavelength changing device.
In the projector disclosed by Patent Literature 1, in shining the excitation light on to the luminescent material layer, the luminescent wheel is driven to rotate by a motor, which generates noises such as a wind noise produced by the rotating luminescent wheel, a high-frequency noise produced by the drive motor, a noise produced by a cooling fan which cools the luminescent wheel, and the like. On the other hand, in the projectors disclosed by Patent Literature 2 and Patent Literature 3, when highly bright excitation light is shone on to the luminescent material, there may be a case where a burned damage is caused, and hence, there is a limit on increasing the brightness of luminescent light.